MIOCENE BEDS — ELEVATION OF SIERRA NEVADA. 21 



almost a marble, or it was found in the valleys near San Francisco bay, in contact with trap 

 and serpentine. With regard to the gneiss, the writer is not inclined to class it with sedi- 

 mentary strata. 



This absence of paUBOzoic,or secondary rock, holds true only of California, south of parallel 

 37°; north of that line a secondary limestone, probably, does exist in the interior and littoral 

 counties. 



The elevation of the Coast Kanges has disclosed a series of middle tertiary beds, above 2,000 

 feet in thickness, possessing fossils in great abundance, some of the species of which are 

 altogether new, and almost all of them new to the tertiaries of this continent, differing in 

 their fauna from what are esteemed coeval beds on the Atlantic slope ; showing that conditions 

 of difference in the waters of both oceans of those periods existed then, though, perhaps, not so 

 marked as now. This itself is remarkable, since at that period of the history of this continent, 

 (i. e., anterior to the elevation of California,) the Pacific ocean must have stretched inland over 

 the Great Basin and Desert, and washed the base of the Wahsatch, or even of the Rocky 

 mountains. The Sierra Nevada then existed as an island, or a series of islands ; and the Pacific 

 thus approaching 400 miles nearer to the Atlantic, which itself spread over the surface of the 

 eastern Atlantic States, both oceans must have been nearer to each other, and had their con- 

 ditions more alike. Yet they must have been sufficiently unlike to produce different varieties 

 of a like species. 



The upheaval of so continuous and lofty a chain as the Sierra Nevada could not have been 

 accomplished without an elevation of the superficial crust upon the east as well as the 

 west side. If, by that elevation, Tulare valley was cut off from its original connection with 

 the country round the head of the Gulf of California, and so upraised as to slope to the Sacra- 

 mento valley, it is not unreasonable to suppose that that action of elevation was propagated to 

 the Great Basin, and that it was also gently lifted out of the waters of the deep. But the 

 mode of elevation of the Great Basin is much more complicated : in Salt Lake valley it is 

 above 4,000 feet over sea level, and on parallel 32° it is at that level, or only a few feet above ; 

 and thence north into Utah it rises by steppes, not by mountain chains, until it attains the 

 upper level, each plateau forming a basin for its own waters. In travelling west, across these 

 upper plateaus, the Sierra Nevada is not the lofty mountains as known in California, on account 

 of the basin level being so much above that of the Sacramento valley. Several thousand feet of 

 altitude are lost to the mountains when viewed from the basin. Something like this occurs in 

 the steppes of Thibet and Tartary, where, travelling south, the Himalaya mountains are apt to 

 be under estimated, because the jjlateau of the steppe country is so elevated ; but, on crossing 

 these mountains into India, the traveller descends several thousand feet, and attains a much 

 lower level of land on the Hindostan side. So it happens in travelling through any of the 

 northern passes of California, at Noble's or Carson's passes, the ascent is comparatively small 

 until the summit is reached, when the descent is more sudden and much greater until the 

 valley is descended. 



Inasmuch as the elevation of the Sierra in the north of California and that of the Cascade 

 mountains of Oregon is much greater than that of the southern portion of the Sierra, it might 

 be supposed that the elevation of the contiguous crust would be in proportion. That if the eleva- 

 tion of the Sierra up to 7,000 feet was sufficient to lift the Colorado desert up to the sea level- 

 as it now stands — then an elevation of the same Sierra to the north to an altitude of 12,000, or 

 even 17,000 feet, might suffice to raise the Great Basin to the level of Salt Lake valley. The ele- 



